Layered (2-D) structure of [Ru2(O2CMe)4]2[Ni(CN)4] determined via Rietveld refinement of synchrotron powder diffraction data

Inorganica Chimica Acta 364 (2010) 172–175

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Layered (2-D) structure of [Ru2(O2CMe)4]2[Ni(CN)4] determined via Rietveld refinement of synchrotron powder diffraction data Jae-Hyuk Her a,1, Peter W. Stephens a,⇑, Bretni S. Kennon b, Chen Liu b, Joel S. Miller b,⇑⇑ a b

Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800, USA Department of Chemistry, University of Utah, Salt Lake City, UT 84112-0850, USA

a r t i c l e

i n f o

Article history: Available online 2 August 2010 Dedicated to Arnold L. Rheingold for his plethora of contributions to Inorganic Chemistry and good friendship

a b s t r a c t Reaction of [Ru2(O2CMe)4]Cl and K2[Ni(CN)4] forms [Ru2(O2CMe)4]2[Ni(CN)4] with the targeted layered structure possessing Ru–N„CANi linkages, albeit strained, with Ru–N„C and Ni–C„N angles in the range of 147–167°. The magnetic properties of [Ru2(O2CMe)4]2[Ni(CN)4] can be fit to a zero-field splitting model with D/kB = 95 K (66 cm1). Ó 2010 Elsevier B.V. All rights reserved.

Keywords: Layer structure X-ray structures Rietveld refinement Ruthenium acetate Nickel complex

1. Introduction Crystallography is at the very basis of solid-state chemistry, as this volume of papers dedicated to the career and accomplishments of Arnie Rheingold testifies. There is a general belief that crystallography requires suitable single crystals (not to take anything away from the skills advanced by Arnie and others to wring information from marginal samples). Recently, powder diffraction has been developing into a technique able to provide decisive information for rather complicated small-molecule crystallographic problems, on a fairly routine basis. In general, structure solution and refinement from powder data require more human effort, and geometric parameters from powder diffraction data have larger error bars than single crystal refinements, if available. But in many cases, such as the present report, the solution of previously unknown structures from powder diffraction enables advances in the understanding of materials. The use of the mixed-valent S = 3/2 [Ru2(O2CMe)4]+ and octahedral [Cr(CN)6]3 building blocks has enabled the deliberate design and construction of a cubic lattice of [Ru2(O2CMe)4]3[Cr(CN)6] composition that magnetically orders as a ferrimagnet [1]. The substitution of pivalate for acetate also led to the expectation of

formation a cubic lattice of [Ru2(O2CBut)4]3[Cr(CN)6] composition, however, only the layered 2-D structural motif could be isolated [2,3]. In order to control the structure of new extended network structures, we sought to deliberately make layered [Ru2(O2CMe)4]2[Ni(CN)4], and herein we report its structure and magnetic properties. 2. Experimental 2.1. Synthesis A 10-mL aqueous solution of 50 mg (0.193 mmol) of K2[Ni(CN)4]H2O (Research Organic/Inorganic, Inc.) was added to a 150 mL methanol solution of 183 mg (0.386 mmol) of [Ru2(O2CMe)4]Cl at room temperature. A brown precipitate appeared immediately and the mixture was stirred for an additional 30 min. The brown precipitate was collected and washed with water and then methanol and dried in vacuum at room temperature. A yellow– brown powder was obtained (yield: 180 mg, 89.7%). IR 2130 s, and 2146 s cm1 (mCN). Anal. Calc. for C20H24NiN4O16Ru4: C, 23.04; H, 2.30; N, 5.38. Found: C, 23.28; H, 2.13; N, 5.44%. Attempts to grow single crystals were unsuccessful.

⇑ Corresponding author. Tel.: +1 631 632 8156; fax: +1 631 632 8176. ⇑⇑ Corresponding author. Tel.: +1 801 585 5455; fax: +1 801 581 8433.

2.2. Crystal structure determination

E-mail addresses: [email protected] (P.W. Stephens), jsmiller@chem. utah.edu (J.S. Miller). 1 Present address: GE Global Research Center, Niskayuna, NY, USA.

High-resolution X-ray powder diffraction patterns were collected at the X16C beamline, National Synchrotron Light Source,

0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2010.07.059

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Brookhaven National Laboratory at ambient temperature. A Si(1 1 1) channel cut monochromator selected a highly collimated incident beam of 0.700252(2) Å. The diffracted X-rays by sample were analyzed by a Ge(1 1 1) single-reflection crystal and detected using NaI scintillation counter. The capillary was spun during data collection for better averaging of the powder pattern data. TOPASAcademic [4] was used to index, solve the structure by direct space searching method (simulated annealing) and refine the structure via Rietveld method. The crystallographic data for [Ru2(O2CMe)4]2[Ni(CN)4] is summarized in Table 1. 2.3. Physical studies Infrared spectra were taken as KBr pellets using a Bruker Tensor 37 FT-IR spectrometer (±1 cm1). Magnetic measurements were made between 5 and 300 K on a Quantum Design MPMS-5XL 5 T SQUID magnetometer equipped with a reciprocating sample measurement system as previously described [5]. The data were corrected for the diamagnetism of the holders. 3. Results and discussion The reaction of [Ru2(O2CMe)4]Cl and K2[Ni(CN)4] forms [Ru2(O2CMe)4]2[Ni(CN)4] whose 2130 and 2146 cm1 mCN absorptions are shifted by 13 ± 5 cm1 to higher energy indicative of [Ni(CN)4]2 bonding to four [Ru2(O2CMe)4]+ cations. While single crystals of the brown precipitate did not form, powder X-ray diffraction was observed, and high-resolution patterns were collected at the National Synchrotron Light Source at ambient temperature (Fig. 1). 3.1. Crystal structure Rietveld refinement of the synchrotron powder diffraction data (Fig. 1) reveals a structure consisting of [Ni(CN)4]2 ions bound to four [Ru2(O2CMe)4]+ cations via two crystallographically independent Ni–C„N–Ru linkages, with Ru–N distances of 2.10(6) and

Table 1 Summary of the synchrotron crystallographic data for [Ru2(O2CMe)4]2[Ni(CN)4]. [Ru2(O2CMe)4]2[Ni(CN)4] Formula C20H24NiN4O16Ru4 Formula mass 1039.5  Space group P1 a (Å) 9.003(1) b (Å) 9.989(1) c (Å) 11.510(1) a (°) 113.78(1) b (°) 114.54(1) c (°) 78.70(1) Z 1 V (Å3) 861.1(5) qcalc (g/cm3) 2.004 Rwpa 0.028 b Rexp 0.016 T (K) 297 k (Å) 0.70025(2) rP ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2ffi calc obs a w ðy yi Þ i i i P , where ycalc Rwp ¼ and yobs are the i i wi ðyobs Þ2 i calculated and i observed intensities at the ith point in the profile, normalized to monitor intensity. The 2 weight wi is 1/r from counting statistics, with the same normalization factor. N is the number of points in the measured profile.ffi rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi b Rexp ¼ P N obs 2 . i

wi ðyi

Þ

Fig. 1. High-resolution synchrotron powder diffraction data () and Rietveld fit for the refined structure of [Ru2(O2CMe)4]2[Ni(CN)4] (–). The lower trace is the difference, measured – calculated, plotted to the same vertical scale.

2.24(3) Å, Ni–C distances of 1.90(2) and 2.07(2) Å, and CN distances of 1.04(2) Å (Fig. 2). Ni–C–N angles are 156(2)° and 167(2)°, the Ru–N–C angles are 147(1)° and 157(2)°. Differences between the inequivalent Ni–CN and Ru–NC bond distances and angles are unexpectedly large; they appear to result from the fact that the Ni ion and the center of the Ru dimer are located on special positions of the lattice, so that their CN linkages must accommodate strain caused by steric interference of the bulky Ru acetate dimers. Thus, the Ru–N–C linkages are not linear, as expected and observed for [Ru2(O2CMe)4]3[Cr(CN)6] and {[Rh2(O2CMe)4]2[Co(CN)6]}3 [6], but are in accord with the 150.5° angle reported for [Ru2(O2 CBut)4]3[Cr(CN)6] [7]. The Ru  Ru distance is 2.270(3) Å in acceptable agreement with 2.282 and 2.290 Å observed for [Ru2(O2 CMe)4]3[Cr(CN)6] and [Ru2(O2CBut)4]3[Cr(CN)6], respectively. The Ni  Ni separations are 11.51 and 12.07 Å within a plane, and 9.00 Å between planes. The layers are 6.51 Å apart from each other (Fig. 3), and the closest non-H interlayer distance is 3.20 Å between acetate C and O atoms. 3.2. Magnetic properties The magnetic susceptibility, v, of [Ru2(O2CMe)4]2[Ni(CN)4] was studied between 2 and 300 K at 500 Oe. The 300 K effective moment [leff = (8vT)1/2], is 5.85 lB per formula unit. This value is close to the expected spin-only value of 5.47 lB for two S = 3/2 [Ru2(O2CMe)4]+ ions. The leff(T) data is fitted to Eq. (1) [8], which has incorporated zero-field splitting (D) and temperature-independent paramagnetism (TIP), (Fig. 4). The Weiss constant, h, is also introduced to account for inter-molecular magnetic interactions. A good fit has been obtained for the effective moment measured as a function of temperature. The fit yielded g = 2.155, D/kB = 95 K (66 cm1), h = 0.15 K and TIP = 0. The D value is in good agreement with other reports although the g value is slightly higher [9].

vRu2

  2D 3 2D 1 þ 3k4DB T 1  e kB T kB T 1 1 þ 9e 2 4  5 þ TIP þ  ¼ 2D kB ðT  hÞ 3 4ð1 þ e2D kB T 1 þ e kB T Þ 3 Ng 2Ru2 l2B

2

ð1Þ

Acknowledgement The authors gratefully acknowledge the initial studies provided by Dr. T.E. Vos, and the support from the NSF (Grant No. 0553573). Use of the National Synchrotron Light Source, Brookhaven National Laboratory, was supported by the US Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.

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Fig. 2. Single layer structure of [Ru2(O2CMe)4]2[Ni(CN)4] viewed perpendicular to the layer (Ru: orange, Ni: silver, O: red, N: blue, C: dark gray, H: light gray). Solid and partially transparent atoms indicate two crystallographically independent groups. Thin black lines define the unit cell boundary. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 3. Packing of adjacent layers of [Ru2(O2CMe)4]2[Ni(CN)4] viewed parallel to the layers and along the c-axis. Hydrogen atoms are omitted for clarity. There are no bonds between layers (blue and red). Ni is green. Similar to Fig. 2, the solid and partially transparent atoms discern two crystallographically independent groups. Thin black lines define the unit cell boundary. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

J.-H. Her et al. / Inorganica Chimica Acta 364 (2010) 172–175

Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.ica.2010.07.059.

5.5

[Ru (O CMe) ] [Ni(CN) ] 2

2

4 2

References

4

eff

Moment, μ , μ

B

6.0

g = 2.155

5.0

-1

D = 95 K (66 cm ) θ = -0.15 K TIP = 0

4.5

4.0

175

0

50

100

150

200

250

300

Temperature, T, K Fig. 4. leff(T) for [Ru2(O2CMe)4]2[Ni(CN)4] (), and a fit to the data with Eq. (1).

Appendix A. Supplementary material CCDC 778327 contains the supplementary crystallographic data for [Ru2(O2CMe)4]2[Ni(CN)4], respectively. These data can be obtained free of charge from The Cambridge Crystallographic data Center via http://www.ccdc.cam.ac.uk/data_request/cif.

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